The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . unnel for exploration, 12 ft. in diameter, was driven acrossthe river, the top being within 2 ft. of the follo\ving maintunnel. The top of the main tunnel excavation in the middleof the river was only 7 ft. from the bed of the Thames, anda temporary blanket of filled earth, usually allowed in similarcases, was prohibited owing to the close proximity of the maximum progress in one day was 12-5 ft., and theaverage in six days 10-4 ft. The air compressors were togethercapable of supplying 1
The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . unnel for exploration, 12 ft. in diameter, was driven acrossthe river, the top being within 2 ft. of the follo\ving maintunnel. The top of the main tunnel excavation in the middleof the river was only 7 ft. from the bed of the Thames, anda temporary blanket of filled earth, usually allowed in similarcases, was prohibited owing to the close proximity of the maximum progress in one day was 12-5 ft., and theaverage in six days 10-4 ft. The air compressors were togethercapable of supplying 1,000,000 cub. ft. of air per hour. Some tunnels of marked importance of this type—to beoperated solely with electric cars—have been built imder theEast and Hudson rivers at New York. Two tubes of 15 diameter and 4150 ft. long penetrate gneiss andgravel directly under the East River between the Batteryand Brooklyn. They were begun in 1902, with Wm. B-Parsons and George S. Rice as engineers, and were finishedin December 1907, under the direction of D. L. Hough of the 4-02 TUNNEL. I Tig. 3.—Cross Sections of Tunnels under Rivers and Harbours. TUNNEL 403 New York Tunnel Company. They carry subway trains. Inone of the blow-outs of compressed air a workman was blownthrough the gravel roof into the river above. He lived untilthe next day. Two other tubes of the same size built also throughgneiss and gravel between 1905 and 1907 by the DegnonContracting Company, with R. A. Shailer as the contractorsengineer, go from 42nd Street to Long Island City. Four much larger tubes (see fig. 3) built in 1904 to 1909, forthe Pennsylvania railroad, with Alfred Noble as chief engineer,S. Pearson & Son as contractors, and E. W. Moir as generalmanager, cross from 32nd and 33rd Streets to Long maximum average progress per day (one heading) for thebest months work was: rock, 4-1 ft.; rock and earth, 38 ft.;earth, with full sand face, 12-8 ft. The best methods of prevent-ing
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectencyclo, bookyear1910
